Casing sealing device



United States Patent 3,486,758 CASING SEALING DEVICE Granison T.Alexander, Jr., Honma, La., assignor to Gem Oil Tool Company, Inc.,Houma, La., a corporation of Louisiana Filed Jan. 18, 1967, Ser. No.610,080 Int. Cl. F16j 1.5/32, /02

US. Cl. 27759 1 Claim ABSTRACT OF THE DISCLOSURE This invention relatesto an apparatus for use in cementing pipe such as a casing in a wellbore to prevent fluid movement along the casing-cement interface.

During oil well drilling operations, quite often it becomes necessary tocement a portion of the casing in the well bore so that production canbe taken from different levels in the well and without the variouslevels contaminating each other. For example, it might be desirable toperforate the casing at one level wherein the formation pressure issubstantially lower than an adjacent level and which adjacent level itis desired to maintain in an unchanged condition. The result is thatthere will be a tendency for the fluid of the higher pressure Zone tomigrate along the pipe at the cement-pipe interface. The seal unit ofthis invention is designed to prevent such migration.

Recent investigations have uncovered the fact that many casing-cementinterfaces have been subjected to bond failure and fluid movementtherepast at lower pressure differentials than is often desired,particularly in depletion type reservoirs or where stimulation(acidizing, fracturing) methods require high injection pressures.Communication at the cement-casing interface, like in the remainder ofthe casing-hole annulus, will prevent efficient depletion of a producingzone or 'cause stimulation work to be ineffective due to uncontrolledmigration in the annulus.

Certain prior art sealing units have been developed in an attempt tosolve this problem, but none of which have been completely successfulfor various reasons including inefiicient stoppage of the migration,early failure, and the like.

It is, therefore, an object of this invention to provide an improvedpipe sealing unit for use in cementing pipe in the well bore, which unitsolves the foregoing problem and overcomes the shortcomings of the priorart.

Briefly stated, this invention includes a lower annular backup member,preferably in the form of a metal ring having an upwardly facingshoulder and having means for fixedly securing the ring about the pipeor casing to be cemented. It also includes an upper annular backupmember, preferably in the form of a metal ring having means for fixedlysecuring the ring about the pipe. A pair of elastomeric annular sealingelements are mounted about the pipe or casing and between the backupmembers, with each of the sealing elements having an annular channelforming a generally U shaped axial end, which ends are mounted in facingrelationship with the opposite ends thereof held in abuttingrelationship with an adjacent backup member. In addition, spacing meansare mounted about the pipe or casing and between the U shaped axial endsof the sealing elements for maintaining a space therebetween. It is tobe understood that a plurality of these sealing units may be used foreach cementing operation and can be axially spaced apart on the casing.

Reference to the drawing will further explain the invention wherein likenumerals refer to like parts and in which:

FIG. 1 is a side elevation view of the apparatus of this invention shownmounted on a casing pipe which casing pipe is shown cemented in a wellbore.

FIG. 2 is a vertical sectional view, somewhat enlarged, of the apparatusshown in FIG. 1.

The apparatus includes a lower annular backup member in the form oflower ring 11 of metal or other suitable material mounted about casingpipe 12 and fixedly held thereto as by a plurality of set screws 13.

The apparatus also includes an upper annular backup member in the formof upper ring 16 of metal or other suitable material which is fixedlysecured about casing 12 at an axially spaced apart position from ring 11and is fixedly secured to casing pipe 12 as by a plurality of set screws13. Lower ring 11 has an upwardly facing abutting surface and upper ring16 has a downwardly facing abutting surface and between said abuttingsurfa ces there is mounted a pair of elastomeric annular sealingelements in the form of upper and lower annular rubber seals 19 and 20.

Each of the seals 19 and 20 have an annular channel forming a generallyU shaped axial end, which form a pair of spaced apart lips, with thelips held in facing relationship. The opposite axial ends of seals 19and 20 are held in abutting relationship with the adjacent abuttingshoulders of metal rings 16 and 11, respectively.

Spacer means are mounted about the pipe and between the U shaped axialends of seals 19 and 20 for maintaining a space therebetween. The spacermeans conveniently take the form of an annular ring 22 having a diametergreater than the outside diameter of pipe 12 and having an axial lengthgreater than the combined depths of the channels in seals 19 and 20,whereby seals 19 and 20 are held in spaced apart relationship.

It is to be understood that spacing ring 22 does not perform a scalingfunction itself and therefore may be perforated or have holes therein,such that fluid pressure may pass therethrough and be applied againsteither the inside or outside lips of each of the seals 19 and 20.

The unit is operated by installation on casing pipe 12 by first slippingupper metal ring 16 over the lower end of pipe 12 and moving it axiallyupward to the desired position where it is secured in place by setscrews 13 in a fixed relationship with pipe 12. Thereafter, upper rubberseal 19, spacer ring 22 and lower seal 20 are fitted over the lower endof pipe 12 and slid up in abutting relationship with upper ring 16, asshown in FIG. 2. Care must be taken to insure that the channels or Ushaped ends ofseals 19 and 20 are facing each other and that ring 22 isinserted in the channels as shown.

Thereafter, lower metal ring 11 is fitted over the end of pipe 12 andmoved up into abutting relationship with lower seal 20 as shown, andthereafter secured fixedly in position by tightening of set screws 13.Wetting the surface of pipe 12 with a soapy solution or diesel oil willfacilitate the sliding of seals 19 and 20 therealong.

In fixedly securing rings 11 and 16 to pipe 12, care must be taken thatthey are spaced uniformly thereabout and the abutting ends thereof aregenerally perpendicular with the circumferential surface of pipe 12.When the unit is to be attached to casing having upset tool joints, itis necessary to stretch seal elements 19 and over the upset and to Weldring halves on opposite sides thereof to form rings 11 and 16.Alternatively, rings 11 and 16 may be formed with hinged halves havingappropriate locking means. Thereafter, the components can be pushedtogether to the position shown in FIG. 2. With the unit thus installed,the casing is run into the bore hole and cemented into place as shown inFIG. 1, by cement 23.

It is to be understood that a plurality of these sealing units can beinstalled on a casing and should preferably be installed immediatelyabove and below the intervals to be perforated. Although the resistanceto fluid flow is not theoretically increased by using multiple units, itis recommended that at least two units be spaced five feet apart andabove the perforation zone and two additional ones also spaced aboutfive feet apart below each zone to allow for possible variation in pipemeasurements, etc. Further, the use of a casing centralizer eitherimmediately above the units or below the units would also assure auniform sheath of cement around the unit as well as providing someprotection to the unit while being run into the hole.

In addition to properly locating the units above and below the zones tobe perforated, the successful operation of the units is further insuredby a good uniform cement job in which both the circulatable andnon-circulatable mud media is effectively displaced by the cement slurryusing proven cementing procedures and equipment, as is well-known tothose skilled in the art.

It is presently thought that the sealing unit as taught herein is moresuccessful than prior art units because of its novel construction. It isthought that the novel arrangement of seals 19 and 20 prevents migrationalong pipe 12 in either the upward direction or downward direction.Lower seal 20 prevents downward migration and upper seal 19 preventsupward migration. It is believed that this occurs becauses any pressurein the space between seals 19 and 20 causes the lips thereof to beprojected radially inwardly and outwardly respectively to scalingengagement with adjacent surfaces. This occurs because of the cup-shapedconstruction of seals 19 and 20 whereby the pressure causes the lips tomove in the radial directions noted above.

Applicants unit does not require special pipe surface preparation suchas sand blasting or chemical removal of mill varnish. It does notrequire excessive differential pressure on the cement (between theannulus and the inside of the casing) while curing.

Applicants unit responds mechanically to any fluid movement from eitherdirection, i.e., above or below.

The mechanical sealing action of applicants invention is not affected bythe thermal expansion and contraction of the pipe due to the cementsheat of hydration while curing.

Since seals 19 and 20 are free from and not attached to the adjacentback up rings 16 and 11 respectively, the seals are able to centerthemselves for efficient sealing.

Applicants sealing unit can be used on upset casing by stretching theelastic seals 19 and 20 over the upset, thereafter splitting andrewelding the steel backup rings 16 and 11 about the pipe and thereafterassembling as shown in FIGS. 1 and 2. Alternatively, and as noted above,hinged backup rings may be used which have appropriate latch means.

What is claimed is:

1. In apparatus sealing fluid flow between a cemented well casing in awell bore and the cement, the combination comprising:

a lower backup ring mounted about said casing, said lower backup ringhaving an upwardly facing shoulder and a plurality of set screws fixedlysecuring said lower backup ring about said casing;

an upper backup ring mounted about said casing, said upper backup ringhaving a downwardly facing shoulder and a plurality of set screwsfixedly securing said upper backup ring about said casing at a positionaxially spaced apart from said lower backup ring;

a pair of unitary elastomeric annular sealing elements mounted aboutsaid casing and between said backup rings, each of said sealing elementshaving an annular channel in one end thereof forming inner and and outerlips, with the lips of one of the said sealing elements supported inspaced apart and facing relationship to the lips of the other of saidsealing elements, said elements being entirely of elastomeric materialand each of said elements having an abutting end opposite from the endhaving said channel, said abutting ends engaging an adjacent one of saidshoulders of said backup rings in nonattached abutting relationship andradially outwardly movable with respect thereto;

and an annular spacer ring mounted about said casing and in saidchannels of said sealing elements and maintaining said spacing betweensaid elements, said annular spacer ring having opening means for passingfluid between opposite sides thereof.

References Cited UNITED STATES PATENTS 3,064,731 11/1962 Hall 166-353,110,346 11/1963 Spurlock et a1. 166-21 FOREIGN PATENTS 571,910 9/ 1945Great Britain.

LAVERNE D. GEIGER, Primary Examiner JEFFREY S. MEDNICK, AssistantExaminer US. Cl. X.R.

